The present invention relates to semiconductor devices and more particularly to trench type power semiconductor devices.
A typical trench type power semiconductor device includes a gate structure, which is supported inside a trench. The gate structure includes a conductive gate electrode insulated from the semiconductor body of the device by an insulation body, which is typically silicon dioxide.
It is well known that a high electric field at the bottom of the trench can compromise the integrity of the device. To overcome this problem, a thick oxide is formed at the bottom of the trench below the gate electrode.
A conventional method for fabricating the thick oxide is by oxidation of the silicon. Oxidation, however, is time consuming, which is costly. In addition, oxidation consumes the silicon. As a result, the cell pitch of the device is adversely affected, thereby adversely affecting the current carrying capability per unit area of the device.